Mr. Durst believed that his expertise in matters of development was being ignored, and he had openly questioned the desire to build housing on the pier, which he told The Villager “doesn’t work.” Part of the problem, Mr. Durst argued, was that additional development would add to the cost of shoring up the piers—the more built up top, the more that must go down below to hold it up. He wanted the trust to spend money now to protect it, but other board members insisted there was no funds for such work.

One person close to the situation said this amounted to “a pissing match” between Mr. Durst and Madelyn Wils, who was appointed president and CEO of the trust in July 2011. “He’s taking his ball and going home,” said the source.

In a statement, Ms. Wils and Friends executive director A.J. Pietrantone said: “The Friends of Hudson River Park and the Hudson River Park Trust are extremely grateful for the many contributions of Douglas Durst and the Durst Organization to Hudson River Park His philanthropy and advocacy for the waterfront and this distinct New York City amenity have had a profound effect on the quality of life for countless New Yorkers.”

Mr. Barowitz said that Mr. Durst, who has not only provided his time to the Friends group but also his money as its biggest donor, would still continue to advocate for the park as a private citizen. Mr. Korman, who could not be reached by The Observer, will attempt the same, as he told Capital New York, which also reported the split.

“With the recent organizational changes made to the Friends, and my growing discomfort with regards to the Trust’s management, I felt that my advocacy would be more effective outside the Friends framework,” Mr. Korman wrote in an email.

Losing two well-to-do backers seems like it could cause a serious blow to the park at a time that it is already desperate for funding, but another Friends board member said it should not have a material impact on the day-to-day operations of the Trust.

In many ways, this is a debate about the nature of how parks get built, maintained and funded in the city. New York has seen a number of public-private parks pop up in the past decade, from Brooklyn Bridge Park to the High Line. The city or state will help pay to build these grand edifices, but unlike Central Park or Prospect Park before them, the city takes little role in the new parks ongoing upkeep. Instead the parks are left to fend for themselves.

(Granted, most ever major open space from Central Park to Bryant Park now has some sort of conservancy, friends group or business improvement district that helps pay a good chunk of the costs for running it, ever since the city began divesting itself of this responsibility in the bankrupt 1970s.)

The argument over who should pay what is playing itself out here, as well. Mr. Durst and Mr. Korman believed the park should front the money to fix Pier 40, and then bring in new tenants to help cover those costs and add to the maintenance kitty going forward. But the bulk of the park’s leadership insists it cannot pay for these fixes up front, and instead wants a private developer to come in and cover them.

In the past, there has been flirtations with everything from building schools here to an outpost for Circ de Soleil, all of which have been defeated for one reason or another, most usually through public outcry. Earlier this year the MLS had even considered it as a possible site for a soccer stadium, but transportation and crowding concerns from the surrounding community quickly stymied that idea.

Among the options the trust would like to see on the table is housing development, currently forbidden by the Hudson River Park Act of 1998, and SHoP Architects was even hired to make a compelling case for such a model earlier this year. The trust insists it is agnostic on which approach would be most suitable, and while housing would probably be the most lucrative—this is housing on the Hudson River waterfront, after all—locals tend to hate residential development, particularly on waterfront plots within public parkland (see: Brooklyn Bridge Park).

The trust has been working for the past year with lawmakers in Albany to try and revise the park act to allow for more types of development. Beyond restricting housing, the legislation limits leases to 29 years, which is seen as too short a time frame to attract a developer who would shoulder the costs of fixing up the pier as part of a larger development package.

But this may be the least of the park’s problems at the moment. It remains without power six weeks after the Sandy storm surge washed over much of the park, including totally flooding Pier 40. “Most of our plants are O.K.,” Ms. Wils said during a panel at a post-Sandy conference hosted by the Municipal Art Socity and Columbia on Thursday. “They’re made to survive underwater, well not underwater, but they can put up with some flooding. I think we lost only five trees and a few plants.”

“The buildings, however, did not fare quite as well,” she said. “We’re still without power, because we are on our own grid, and we’ve had to work on our own to restore that.”

Meanwhile, there is some positive development news, as Pier 57, a cultural and shopping hub also long in the works at 15th Street, won approval from the local community board earlier this month. It will offer activities and access to the pier, as well as desperately needed funds to the park.

Whether something similar will get built at Pier 40, especially before the structure should deteriorate beyond repair, remains to be seen.

“Despite these and other challenges, including the recent impact of Superstorm Sandy, the Friends and the Trust remain wholly committed to working together to secure resources for the Park and sustaining its future,” Ms. Wils and Mr. Pietrantone concluded their statement.

“Now with Douglas out of the way, the trust can start to work cohesively on fixing this pier,” said the park source. The trust just has to convince Albany, and its angry neighbors, of the same thing.

Correction:A previous version of this story said the new acting board chair was Jason Sadrian, not Justin Sadrian. The Observer regrets the error.